Re: 818 630 gearbox rebuild

thank you very much for the pictures and explanation. i'm sure it will be very helpful to future readers. i'm curious though, what was the original tolerance spec on the bearings? you say you went to c3 but didn't mention what they were.

Re: 818 630 gearbox rebuild

Originally Posted by bmarler

thank you very much for the pictures and explanation. i'm sure it will be very helpful to future readers. i'm curious though, what was the original tolerance spec on the bearings? you say you went to c3 but didn't mention what they were.

The bearings part numbers where

on pinion 6207
on layshaft 6206 and nu 305

There where no other numbering apart from the RIV part number(4A) on the 6207 bearing.
Spare parts catalogue also only states 6206 / 6207 / nu 305

I may have not been very clear in my previous posts regarding this.

I decided on C3 bearing tolerance , which is actually slightly "looser" than a standard bearing for example.
The new bearing did however "FEEL" ever so slightly "tigher" than the old one which could be from some wear at the age they where. Or my imagination since i think it is very hard to feel the state of a bearing.

I cannot however give a really good reason for the C3 decision apart from my gut says it makes sense. It is awfully large bearings for something that will frequently run at same rpm as engine at highway speeds for the pinion.

But I am in no way saying use c3 bearings in your gearbox. That is something I decided to do.

Re: 818 630 gearbox rebuild

You got to take thermal expansion coefficients in mind too. The gearbox gets warmed up, and it can get quite hot in there. If the coefficients are not the same for the different parts, you got to take that into account, and leave a bit for the expansion.

Re: 818 630 gearbox rebuild

it's easy to defeat the syncros when shifting these boxes, especially when cold. take your time on the 1-2 shift, that's the easiest to grind. you might have a worn syncro, or a bent shift fork, or any number of things. but keep in mind the reviews of the cars when new mentioned this.
lots of folks switched to full synth gear lube and this seems to help a bit. i use a redline product and it works good but i still have to let the box warm up before any aggressive shifting.

Re: 818 630 gearbox rebuild

Originally Posted by bmarler

it's easy to defeat the syncros when shifting these boxes, especially when cold. take your time on the 1-2 shift, that's the easiest to grind. you might have a worn syncro, or a bent shift fork, or any number of things. but keep in mind the reviews of the cars when new mentioned this.
lots of folks switched to full synth gear lube and this seems to help a bit. i use a redline product and it works good but i still have to let the box warm up before any aggressive shifting.

If this is a semi-normal thing I may just leave the gearbox well enough alone.. I noticed the grinding and after a couple times, just adjusted the way I drive/shift to avoid it happening. Especially with how short the 1st gear is, I typically didn't really need it unless I was coming to a full stop anyway.

Also, I will try changing the gear lube.. The gear lube is probably quite old at this point. I changed the engine oil but hadn't bothered to change the gear oil because I knew the box was coming out of the car anyway.

Re: 818 630 gearbox rebuild

didn't really mean grinding, just a little crunchy shifting. it's pretty well known that these boxes need to be shifted with care when cold. folks that are used to modern gearboxes may have to adjust their shifting style. possibly double de-clutching if needed.